Broadband faraday rotator

Abstract

An apparatus includes a dispersive-collimating element, a Faraday material apparatus and a focusing-dispersive element. The dispersive-collimating element assigns each beam wavelength to a particular spatial position. The beams are parallel one to the other. The Faraday material apparatus provides a polarization rotation independently for each wavelength, and the focusing-dispersive element recombines the different wavelengths into one single beam.

The invention claimed is: 
     
       1. An apparatus comprising:
 a dispersive-collimating element, a Faraday material apparatus and a focusing-dispersive element such that said dispersive-collimating element assigns each beam wavelength to a particular spatial position, the beams being parallel one to the other, said Faraday material apparatus provides a polarization rotation independently for each wavelength, and said focusing-dispersive element recombines the wavelengths into one single beam, wherein said Faraday material apparatus comprises a Faraday material with a non-zero Verdet coefficient located within a magnetic field so that each wavelength propagates for a different length within the Faraday material so as to generate a polarization rotation that is the same for all the wavelengths, and wherein a shape of the Faraday material is complemented to a rectangular shape by a transparent material with a near-zero Verdet coefficient and index-matched to a refractive index of the Faraday material, so that beams exit in a direction that is parallel to the impinging beam. 
 
     
     
       2. The apparatus according to  claim 1 , wherein in said dispersive-collimating element there are curved surfaces that are preceded, followed or both preceded and followed by spatially variable birefringent elements so that polarization is not distorted by interaction with the curved surfaces. 
     
     
       3. The apparatus according to  claim 1 , wherein a length of the Faraday material is modified for each wavelength. 
     
     
       4. An apparatus comprising:
 a dispersive-collimating element, a Faraday material apparatus and a focusing-dispersive element such that said dispersive-collimating element assigns each beam wavelength to a particular spatial position, the beams being parallel one to the other, said Faraday material apparatus provides a polarization rotation independently for each wavelength, and said focusing dispersive element recombines the wavelengths into one single beam, wherein said Faraday material apparatus comprises a Faraday material with a non-zero Verdet coefficient located within a magnetic field so that each wavelength propagates for a different length within the Faraday material so as to generate a polarization rotation that is the same for all the wavelengths, and wherein a shape of the Faraday material is complemented to a rectangular shape by using a complemented part of said Faraday material, and distanced from said Faraday material by a transparent material with a near-zero Verdet coefficient and index-matched to a refractive index of the Faraday material, and said complemented part is located in a region where the magnetic field is approximately null. 
 
     
     
       5. The apparatus according to  claim 4 , wherein in said dispersive-collimating element there are curved surfaces that are preceded, followed or both preceded and followed by spatially variable birefringent elements so that polarization is not distorted by interaction with the curved surfaces. 
     
     
       6. The apparatus according to  claim 4 , wherein a length of the Faraday material is modified for each wavelength.